NL2006228A

NL2006228A - Alignment mark, substrate, set of patterning devices, and device manufacturing method.

Info

Publication number: NL2006228A
Application number: NL2006228A
Authority: NL
Inventors: David Deckers; Sami Musa
Original assignee: Asml Netherlands Bv
Priority date: 2010-03-17
Filing date: 2011-02-17
Publication date: 2011-09-20
Also published as: JP5312501B2; JP2011199282A; US9025148B2; US20120057159A1

Description

ALIGNMENT MARK, SUBSTRATE, SET OF PATTERNING DEVICES, AND DEVICE

MANUFACTURING METHOD

BACKGROUND

Field of the Invention

The present invention relates to an alignment mark, a substrate, a set of patterning devices, and a method for manufacturing a device.

Description of the Related Art A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In such a case, a patterning device, which is alternatively referred to as a mask or a reticle, may be used to generate a circuit pattern to be formed on an individual layer of the IC. This pattern can be transferred onto a target portion (e.g. including part of, one, or several dies) on a substrate (e.g. a silicon wafer). Transfer of the pattern is typically via imaging onto a layer of radiation-sensitive material (resist) provided on the substrate. In general, a single substrate will contain a network of adjacent target portions that are successively patterned. Conventional lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion at once, and so-called scanners, in which each target portion is irradiated by scanning the pattern through a radiation beam in a given direction (the “scanning”-direction) while synchronously scanning the substrate parallel or anti-parallel to this direction. It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate.

In practice, multiple patterns may be projected on top of each other to obtain a three dimensional product structure. It is of importance that the multiple patterns are properly aligned with respect to each other. This overlay requirement is increasingly important with increasing resolution.

In lithography processes, double patterning methods such as Litho Etch, Litho Freeze, etc., may be used. An important reason for using such techniques is to enhance feature density on the substrate.

With these techniques alignment of the first and second exposure on product resolution level has become even more important. Therefore, there is a need for a system and a method to determine alignment of a first and second exposure on both a macro level, as for instance used in conventional alignment measurement tools, and a micro level, for instance at product resolution level.

Several methods and measurement tools are available to measure overlay of multiple exposures. However, different methods and tools are suitable for different measurement ranges, and the measurement techniques of the different methods and tools cannot be (directly) compared.

SUMMARY

It is desirable to provide an alignment mark which can be used to determine alignment of multiple exposures at two magnitude levels (e.g. at macro level and at micro level) at a single location.

According to an embodiment of the invention, there is provided an alignment mark which is configured and arranged to determine alignment of a first and a further exposure on a substrate on a macro level and/or a micro level, said alignment mark comprising a first alignment pattern projected during the first exposure and a second alignment pattern projected during the further exposure, wherein said alignment mark comprises a first sub-mark at least partially defined by said first alignment pattern and a second sub-mark at least partially defined by said second alignment pattern, wherein relative positions of said first and second sub-marks on said substrate are representative for alignment of the first and further exposures on the macro level, and wherein at least one submark at least partially is defined by image lines of said first alignment pattern and said second alignment pattern, wherein a part of the image lines is projected during the first exposure and a part of the image lines is projected during the further exposure, and wherein relative positions of image lines of said first alignment pattern and image lines of said second alignment pattern of said at least one sub-mark are representative for alignment of the first and second exposures on the micro level.

According to an embodiment of the invention, there is provided a substrate comprising an alignment mark to determine alignment of a first and a further exposure on a substrate on a macro level and/or a micro level, said alignment mark comprising a first alignment pattern projected during the first exposure and a second alignment pattern projected during the further exposure, wherein said alignment mark comprises a first sub-mark at least partially defined by said first alignment pattern and a second sub-mark at least partially defined by said second alignment pattern, wherein relative positions of said first and second sub-marks on said substrate are representative for alignment of the first and further exposures on the macro level, and wherein at least one submark at partially is defined by image lines of said first alignment pattern and said second alignment pattern, wherein a part of the image lines is projected during the first exposure and a part of the image lines is projected during the further exposure, and wherein relative positions of image lines of said first alignment pattern and image lines of said second alignment pattern of said at least one sub-mark are representative for alignment of the first and second exposures on the micro level.

According to an embodiment of the invention, there is provided a set of patterning devices for use in a lithographic process, comprising: a first patterning device having a first alignment pattern to be projected on a substrate during a first exposure as part of an alignment mark, and a second patterning device having a second alignment pattern to be projected on said substrate during a further exposure as part of the same alignment mark, wherein said first alignment pattern at least partially defines a first sub-mark of said alignment mark, and wherein said second alignment pattern at least partially defines a second sub-mark of said alignment mark, wherein relative positions of the first and second sub-marks on said substrate are suitable to determine alignment of the first and further exposures on a macro level, and wherein said first alignment pattern and said second alignment pattern in combination define at least one sub-mark which is at least partially defined by image lines of said first alignment pattern and said second alignment pattern, wherein a part of the image lines is projected during the first exposure and a part of the image lines is projected during the further exposure, wherein relative positions of image lines of said first alignment pattern and said second alignment pattern of said at least one sub-mark on said substrate are suitable to determine alignment of the first and further exposures on a micro level.

According to an embodiment of the invention, there is provided a device manufacturing method comprising: transferring during a first exposure a pattern from a first patterning device onto a substrate, transferring during a further exposure a pattern from a second patterning device onto said substrate, wherein said first patterning device comprises a first alignment pattern projected during said first exposure as part of an alignment mark on said substrate, and wherein said second patterning device comprises a second alignment pattern projected during the further exposure as part of the same alignment mark, wherein said first alignment pattern at least partially defines a first sub-mark of said alignment mark, and wherein said second alignment pattern at least partially defines a second sub-mark of said alignment mark, and wherein said first alignment pattern and said second alignment pattern in combination define at least one sub-mark, determining alignment of the first and further exposures on a macro level by comparison of relative positions of the first and second sub-marks on said substrate, and determining alignment of the first and further exposures on a micro level by comparison of relative positions of image lines of said first alignment pattern and said second alignment pattern within said at least one sub-mark on said substrate, BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:

Figure 1 depicts a lithographic apparatus according to an embodiment of the invention;

Figure 2 depicts schematically the projection of two alignment patterns of a target mark on a set of patterning devices onto a substrate to form on the substrate an alignment mark according to the invention;

Figure 3 depicts an example of a macro level prior art alignment mark;

Figure 4 depicts an alignment mark design according to the invention based on the alignment mark of Figure 3;

Figures 5a, 5b, and 5c depict cross sections of substrates before a second exposure in a double patterning process; and

Figure 6 depicts an alternative example of a macro level prior art alignment mark;

Figure 7 depicts an alignment mark design according to the invention based on the alignment mark of Figure 6;

DETAILED DESCRIPTION

Figure 1 schematically depicts a lithographic apparatus according to one embodiment of the invention. The apparatus includes an illumination system (illuminator) IL configured to condition a radiation beam B (e.g. UV radiation or any other suitable radiation), a mask support structure (e.g. a mask table) MT constructed to support a patterning device (e.g. a mask) MA and connected to a first positioning device PM configured to accurately position the patterning device in accordance with certain parameters. The apparatus also includes a substrate table (e.g. a wafer table) WT or "substrate support" constructed to hold a substrate (e.g. a resist-coated wafer) W and connected to a second positioning device PW configured to accurately position the substrate in accordance with certain parameters. The apparatus further includes a projection system (e.g. a refractive projection lens system) PS configured to project a pattern imparted to the radiation beam B by patterning device MA onto a target portion C (e.g. including one or more dies) of the substrate W.

The illumination system may include various types of optical components, such as refractive, reflective, magnetic, electromagnetic, electrostatic or other types of optical components, or any combination thereof, for directing, shaping, or controlling radiation.

The mask support structure supports, i.e. bears the weight of, the patterning device. It holds the patterning device in a manner that depends on the orientation of the patterning device, the design of the lithographic apparatus, and other conditions, such as for example whether or not the patterning device is held in a vacuum environment. The mask support structure can use mechanical, vacuum, electrostatic or other clamping techniques to hold the patterning device.

The mask support structure may be a frame or a table, for example, which may be fixed or movable as required. The mask support structure may ensure that the patterning device is at a desired position, for example with respect to the projection system. Any use of the terms “reticle” or “mask” herein may be considered synonymous with the more general term “patterning device.”

The term “patterning device” used herein should be broadly interpreted as referring to any device that can be used to impart a radiation beam with a pattern in its cross-section so as to create a pattern in a target portion of the substrate. It should be noted that the pattern imparted to the radiation beam may not exactly correspond to the desired pattern in the target portion of the substrate, for example if the pattern includes phase-shifting features or so called assist features. Generally, the pattern imparted to the radiation beam will correspond to a particular functional layer in a device being created in the target portion, such as an integrated circuit.

The patterning device may be transmissive or reflective. Examples of patterning devices include masks, programmable mirror arrays, and programmable LCD panels. Masks are well known in lithography, and include mask types such as binary, alternating phase-shift, and attenuated phase-shift, as well as various hybrid mask types. An example of a programmable mirror array employs a matrix arrangement of small mirrors, each of which can be individually tilted so as to reflect an incoming radiation beam in different directions. The tilted mirrors impart a pattern in a radiation beam which is reflected by the mirror matrix.

The term “projection system” used herein should be broadly interpreted as encompassing any type of projection system, including refractive, reflective, catadioptric, magnetic, electromagnetic and electrostatic optical systems, or any combination thereof, as appropriate for the exposure radiation being used, or for other factors such as the use of an immersion liquid or the use of a vacuum. Any use of the term “projection lens” herein may be considered as synonymous with the more general term “projection system”.

As here depicted, the apparatus is of a transmissive type (e.g. employing a transmissive mask). Alternatively, the apparatus may be of a reflective type (e.g. employing a programmable mirror array of a type as referred to above, or employing a reflective mask).

The lithographic apparatus may be of a type having two (dual stage) or more substrate tables or "substrate supports" (and/or two or more mask tables or "mask supports"). In such “multiple stage” machines the additional tables or supports may be used in parallel, or preparatory steps may be carried out on one or more tables or supports while one or more other tables or supports are being used for exposure.

The lithographic apparatus may also be of a type wherein at least a portion of the substrate may be covered by a liquid having a relatively high refractive index, e.g. water, so as to fill a space between the projection system and the substrate. An immersion liquid may also be applied to other spaces in the lithographic apparatus, for example, between the mask and the projection system. Immersion techniques can be used to increase the numerical aperture of projection systems. The term “immersion” as used herein does not mean that a structure, such as a substrate, must be submerged in liquid, but rather only means that a liquid is located between the projection system and the substrate during exposure.

Referring to figure 1, the illuminator IL receives a radiation beam from a radiation source SO. The source and the lithographic apparatus may be separate entities, for example when the source is an excimer laser. In such cases, the source is not considered to form part of the lithographic apparatus and the radiation beam is passed from the source SO to the illuminator IL with the aid of a beam delivery system BD including, for example, suitable directing mirrors and/or a beam expander. In other cases the source may be an integral part of the lithographic apparatus, for example when the source is a mercury lamp. The source SO and the illuminator IL, together with the beam delivery system BD if required, may be referred to as a radiation system.

The illuminator IL may include an adjuster AD configured to adjust the angular intensity distribution of the radiation beam. Generally, at least the outer and/or inner radial extent (commonly referred to as σ-outer and σ-inner, respectively) of the intensity distribution in a pupil plane of the illuminator can be adjusted. In addition, the illuminator IL may include various other components, such as an integrator IN and a condenser CO. The illuminator may be used to condition the radiation beam, to have a desired uniformity and intensity distribution in its cross-section.

The radiation beam B is incident on the patterning device (e.g., mask MA), which is held on the mask support structure (e.g., mask table MT), and is patterned by the patterning device. Having traversed the mask MA, the radiation beam B passes through the projection system PS, which focuses the beam onto a target portion C of the substrate W. With the aid of the second positioning device PW and position sensor IF (e.g. an interferometric device, linear encoder or capacitive sensor), the substrate table WT can be moved accurately, e.g. so as to position different target portions C in the path of the radiation beam B. Similarly, the first positioning device PM and another position sensor (which is not explicitly depicted in Figure 1) can be used to accurately position the mask MA with respect to the path of the radiation beam B, e.g. after mechanical retrieval from a mask library, or during a scan. In general, movement of the mask table MT may be realized with the aid of a long-stroke module (coarse positioning) and a short-stroke module (fine positioning), which form part of the first positioning device PM. Similarly, movement of the substrate table WT or "substrate support" may be realized using a long-stroke module and a short-stroke module, which form part of the second positioner PW. In the case of a stepper (as opposed to a scanner) the mask table MT may be connected to a short-stroke actuator only, or may be fixed. Mask MA and substrate W may be aligned using mask alignment marks Ml, M2 and substrate alignment marks PI, P2. Although the substrate alignment marks as illustrated occupy dedicated target portions, they may be located in spaces between target portions (these are known as scribe-lane alignment marks). Similarly, in situations in which more than one die is provided on the mask MA, the mask alignment marks may be located between the dies.

In Figure 1, a set of two masks MA is shown. These two masks may for instance be used for a double patterning technique, wherein during a first exposure, the pattern of the first mask is projected on the substrate W, and, during a second exposure, the pattern of the second mask is projected on the substrate W. Each of the masks MA comprises in addition to the alignment marks Ml, M2, an alignment pattern M3a, M3b. The alignment patterns M3a and M3b may be different. The alignment patterns M3a, M3b are projected on the substrate to form the alignment mark M3p. The comparison of the relative positions of the alignment patterns M3a, M3b as projected in the alignment mark M3p provides information of the relative positions of the patterns projected during the second exposure with respect to the patterns projected during the second exposure.

The alignment mark M3p formed by alignment patterns M3a, M3b provides information of alignment on macro level, but also of alignment on micro level. The terms “macro level” and “micro level” are used to indicate the relative relation between the two levels on which the alignment is determined, but does not necessarily relate to absolute ranges. The terms ‘macro level’ and ‘micro level’ are used to indicate the size of the measurement range comprising the features of the alignment mark that are used to determine alignment of the multiple exposures. However, both macro level and micro level design may be used to determine alignment of exposures with the same accuracy, for instance product resolution.

The macro level may for instance be in a range larger than 200 nm, preferably between 0,5 pm and 5 pm. The micro level is preferably about the same as the production resolution. This production resolution may be in a range smaller than 150 nm, preferably between 5 nm and 100 nm.

Furthermore, the alignment patterns M3a, M3b are chosen such that the macro level alignment and micro level alignment may be determined by using any possible technique, such as an optical or diffraction based technique.

The macro level alignment may for example be determined by scatterometry techniques (e.g. such as spectroscopic scatterometry or angle-resolved scatterometry), or by a method using a lithographic apparatus, while the micro level alignment may be determined by a method using measurements performed on a CD-SEM (Critical Dimension - Scanning Electron Microscopy).

The alignment patterns M3a, M3b, and the resulting alignment mark may be realized as shown in Figure 2, 4 or 7, but also other suitable alignment patterns may be applied.

In an embodiment of the invention a known macro level target mark design is used. Such known target mark design may comprise at least a first sub-mark projected during the first exposure and a second sub-mark projected during the second exposure, wherein the relative positions of the projected first sub-mark and second sub-mark provide alignment information on macro level.

In a target mark according to the invention at least one of the sub-marks of the know target mark is sub-segmented into image lines, wherein a part of the image lines is projected during the first exposure and a part of the image lines during the second exposure. As a result, the respective sub-mark may be used to obtain alignment information on micro level. Thus one submark may be used for both macro level and micro level alignment information.

It is to be noted that in general for an embodiment of an alignment target according to the invention a part of the image lines is projected during a first exposure and a part of the image lines is projected during a further exposure. As will be understood by a person skilled in the art for double patterning processes the further exposure as mentioned before is usually the second exposure .

It is remarked that the term “image lines” is used to describe parts of the alignment pattern. These image lines do not have to be elongate lines, but may also have any other shape suitable to be used in an alignment pattern. An embodiment of an alignment mark according to the invention comprises at least one sub-mark which is at least partially defined by image lines of the first alignment pattern and the second alignment pattern. In other words, an alignment mark according to the invention comprises at least one sub-mark, which is at least partially defined by either said first alignment pattern or by said second alignment patten, while the sub-mark is subsegmented by image lines from either the second alignment pattern or the first alignment pattern, respectively.

In an embodiment, as described above, the sub-segmented sub-mark is one or more of the sub-marks used for macro level alignment information, and preferably all sub-marks are subsegmented. However, the target mark according to the invention may also comprise two or more sub-marks for macro level alignment information and one or more other sub-segmented submarks for micro level alignment information.

In an embodiment, the outer circumference of a sub-segmented sub-mark is formed mainly, preferably completely, by image lines of one of the alignment patterns, since this outer circumference is used to determine macro alignment information. In such embodiment, image lines of one of said first and second alignment pattern define an array of rectangular cells, and lines of the other of said first and second alignment pattern define a line within each of said rectangular cells.

The lithographic apparatus as depicted in Figure 1 could be used in at least one of the following modes: 1. In step mode, the mask table MT or "mask support" and the substrate table WT or "substrate support" are kept essentially stationary, while an entire pattern imparted to the radiation beam is projected onto a target portion C at one time (i.e. a single static exposure). The substrate table WT or "substrate support" is then shifted in the X and/or Y direction so that a different target portion C can be exposed. In step mode, the maximum size of the exposure field limits the size of the target portion C imaged in a single static exposure.

2. In scan mode, the mask table MT or "mask support" and the substrate table WT or "substrate support" are scanned synchronously while a pattern imparted to the radiation beam is projected onto a target portion C (i.e. a single dynamic exposure). The velocity and direction of the substrate table WT or "substrate support" relative to the mask table MT or "mask support" may be determined by the (de-)magnification and image reversal characteristics of the projection system PS. In scan mode, the maximum size of the exposure field limits the width (in the nonscanning direction) of the target portion in a single dynamic exposure, whereas the length of the scanning motion determines the height (in the scanning direction) of the target portion.

3. In another mode, the mask table MT or "mask support" is kept essentially stationary holding a programmable patterning device, and the substrate table WT or "substrate support" is moved or scanned while a pattern imparted to the radiation beam is projected onto a target portion C. In this mode, generally a pulsed radiation source is employed and the programmable patterning device is updated as required after each movement of the substrate table WT or "substrate support" or in between successive radiation pulses during a scan. This mode of operation can be readily applied to maskless lithography that utilizes programmable patterning device, such as a programmable mirror array of a type as referred to above.

Combinations and/or variations on the above described modes of use or entirely different modes of use may also be employed.

Figure 2 shows a possible embodiment of an alignment target according to the invention. The top left side of Figure 2 shows a circular part of a patterning device 1 comprising a first alignment pattern 2. The top right side of Figure 2 shows a circular part of a patterning device 3 comprising a second alignment pattern 4. The set of patterning devices 1, 3 further comprises projection patterns to be projected on a number of substrates 5. The patterning devices 1, 3 may be suitable for a double patterning process. A double patterning process may be used for increasing the feature density on the substrate.

To check the alignment of the first exposure of the first patterning device 1 and the second exposure of the second patterning device 3 with respect to each other, the alignment patterns 2, 4 are provided. It is remarked that the alignment pattern 4 is shown in dashed lines to see the difference between the alignment pattern 2 of the patterning device 1, and the alignment pattern 4 of the patterning device 3. The actual alignment pattern 4 may comprise solid lines.

During the first and second exposures the alignment patterns 2, 4 are projected on a part of the substrate 5, as shown at the bottom side of Figure 2, to form an alignment mark 6, which is representative for the alignment of the first and second exposure on both macro level and micro level.

The alignment patterns 2, 4 form two sub-marks 7, 8. The outer circumference of the submark 7 is formed by the first alignment pattern 2, while the outer circumference of the second sub-mark 8 is formed by the second alignment pattern 4. Within the image lines of the alignment pattern 2 of the sub-mark 7, image lines of the second alignment pattern 4 are provided, while within the image lines of the alignment pattern 4 of the sub-mark 8 image lines of the first alignment pattern 2 are provided. Thus the image lines of the first alignment pattern 2 enclose the image lines of the second alignment pattern 4 in sub-mark 7 and vice versa the image lines of the second alignment pattern 4 enclose the image lines of the first alignment pattern 2 in submark 8.

Within the measurement area range 9, i.e. the macro level measurement range, the alignment of the first exposure and the second exposure may be determined on macro level by comparison of the relative positions of the two sub-marks 7, 8. Since typically the outer circumferences of the sub-marks 7, 8 will be compared, the comparison of the relative positions of the sub-marks 7, 8 corresponds to comparison of the positions of the first alignment pattern 2 and the second alignment pattern 4.

Within the measurement area 10, i.e. the micro level measurement range, the alignment of the first and second exposure may be determined on a micro level by comparison of the alignment patterns 2, 4 within the sub-mark 8. Correspondingly, the alignment between the first and the second exposures may also be determined by comparison between the alignment patterns 2, 4 within the sub-mark 7. The relative positions of the alignment pattern 2, 4 within the submarks 7, 8 may for instance be determined by a method using measurements performed on a CD-SEM.

Figure 3 shows a prior art conventional bar-in-bar alignment mark 100 which is used to determine alignment on macro level by comparison of the relative position of the sub-marks.

Such bar-in-bar design may be used in a measurement method to determine alignment of two subsequent exposures.

The alignment mark 100 is formed from four outer bar-shaped sub-marks 101 projected in a first exposure, and four inner bar-shaped sub-marks 102 projected in a second exposure. The relative positions of the sub-marks 101 and sub-marks 102 may be measured to determine the alignment of the first and the second exposure. The thickness of the bars of the substrate is about 2 pm, and thus the macro level range in which alignment can be determined is in substantially the same range for instance 2-10 pm.

Instead of the shown bar-in-bar design, the alignment mark may also comprise a number of differently positioned sub-marks projected in different exposures such that the relative positions are representative for the alignment of the first and the second exposure.

In an embodiment of the invention such conventional design may be used for the design of an alignment mark of the invention.

Figure 4 shows an alignment mark design 20 based on the conventional design of Figure 3.

In the embodiment of Figure 4, each of the sub-marks 21, 22 is sub-segmented in a part which is projected during the first exposure (shown in solid lines), and a part which is projected during the second exposure (shown in dashed lines). Each sub-segmentation is chosen such that the outer circumference of each sub-mark is formed by one of the exposures. By creating the outer circumference of the sub-marks at the relevant side, preferably mainly and more preferably completely from one exposure, the conventional measurement method in which the relative positions of the sub-marks 21, 22 are compared, can reliably be maintained.

The size of the image lines within the sub-marks 21, 22 are chosen such that the product resolution of the actual product is resembled, for instance in the range 10 nm to 150 nm. As a result, alignment of the first and second exposure on product resolution level, i.e. micro level, can be determined within each of the sub-marks 21, 22. Therefore, in an alternative embodiment, only a part or even one of the sub-marks 21, 22 of the conventional design may be subsegmented to obtain an alignment mark according to the invention.

The alignment mark of Figure 4 makes alignment measurements on macro level and micro level with the same alignment mark and at the same location possible.

In an alternative embodiment, any other conventional alignment mark comprising a number of sub-marks may be used for the design of an alignment mark according to the invention. By sub-segmentation of at least one of the sub-marks in a part projected in the first exposure and a part projected in the second exposure, the conventional alignment mark may be made suitable for the conventional overlay measurement on macro level by comparison of the relative positions of the sub-marks and a further overlay measurement on micro level by comparison of the relative positions of the alignment patterns of the first exposure and the second exposure within a sub-mark.

With reference to Figures 5a, 5b and 5c another advantage of the sub-segmentation of the sub-marks 21, 22 will be discussed. In some double patterning processes a photo-resistive layer is provided on the substrate between the two exposures. This layer is typically brought on the substrate by spinning the photo resistive layer material over the substrate surface after the first exposure. The photo-resistive material is attracted by the parts of the substrate on which the patterned beam is projected, i.e. the pattern projected on the substrate. When the distance between adjacent projected lines is relative small, such as usually is the case in the product pattern, the photo-resistive layer will be planar. When the distance is larger as in the case in conventional alignment targets the photo-resistive layer may show height differences.

Figure 5a shows a part of the substrate 50 with a first photo-resistive layer 51 on which a pattern 52 is projected during a first exposure. A second photo-resistive layer 53 is provided on the substrate before the second exposure. The pattern of the second exposure is not shown. Since the resolution of the product pattern is relatively high, the second photo-resistive layer is equally attracted over the surface of the substrate and as a result planar. The optimal focus height F for the combination of the first and second photo-resistive layer for the second exposure is indicated in Figure 5a by a dashed line.

In Figure 5b, a cross section after the first exposure of the conventional target of Figure 3 is shown along line A-A, i.e. sub-marks 101 are projected, but the sub-mark 102 is not yet projected on the substrate 50. After exposure in the first photo-resistive layer 51, a second photoresistive layer 53 is provided on the substrate 50. Since the location where the sub-mark 102 is to be projected on the substrate 50, the second photo-resistive layer 53 is substantially lower at this location, or even not present. As a result, the optimal focus height F for the second exposure of the sub-mark 102 is substantially lower than the optimal focus height for product features. Since the best-focus exposure conditions are determined on product features, the second exposure of the alignment target will be printed out-of-focus, resulting in less reliable alignment measurements.

In Figure 5c, a similar cross section after the first exposure on the substrate 50 of the alignment mark of Figure 4 along line B-B is shown. After the first exposure in the first photo resistive layer 51, a part of all the sub-marks 21, 22 will be projected. As a result, the second photo-resistive layer 53 will be provided on all locations of the sub-marks 21,22. Thus, in the areas where further parts of the sub-marks 21, 22 will be projected during the second exposure, a planar second photo-resistive layer 53 will be provided which will have substantially the same height as the second photo-resistive layer 53 on the product pattern of the substrate. Therefore, the optimal focus height F for the second exposure of the alignment mark substantially corresponds with the optimal focus height F of the product pattern, and the second exposure of the alignment mark can accurately be printed on the substrate.

Thus, sub-segmentation of each of the sub-marks in a part projected during the first exposure and a part projected in the second exposure, obviates focus problems due to different heights of the second photo-resistive layers in product and alignment mark areas of the substrates in certain double patterning processes. It is remarked that the focus problems may also be taken away by sub-segmentation of the sub-marks which conventionally are only projected in the first exposure.

Figure 6 shows another prior art conventional macro level alignment mark 110. This known design, may be used in a measurement method to determine alignment of two subsequent exposures.

The alignment mark 110 design comprises bar-shaped sub-marks 111 projected in a first exposure, and bar-shaped sub-marks 112 projected in a second exposure. The relative positions of the sub-marks 101 and sub-marks 102 may be measured to determine the alignment of the first and the second exposure on macro level.

Instead of the shown bar-in-bar design, the alignment mark may also comprise a number of differently positioned sub-marks projected in different exposures such that the relative positions are representative for the alignment of the different exposures with respect to each other.

Figure 7 shows an alignment mark design 30 based on the conventional design of Figure 6.

In the embodiment of Figure 7, each of the sub-marks is sub-segmented in a part which is projected during the first exposure (shown in solid lines), and a part which is projected during the second exposure (shown in dashed lines). Each sub-segmentation is chosen such that the outer circumference of each sub-mark is formed by one of the exposures. By creating the outer circumference of the sub-marks at the relevant side, preferably mainly and more preferably completely from one exposure, the conventional measurement method on macro level in which the relative positions of the sub-marks 31, 32 are compared, can reliably be maintained.

The size of the image lines within the sub-marks 31,32 are chosen such that the product resolution of the actual product is resembled, for instance in the range 5 nm to 150 nm. As a result, alignment of the first and second exposure micro level can be determined within each of the sub-marks 31, 32. Therefore, in an alternative embodiment, only a part or even one of the sub-marks 31, 32 of the conventional design may be sub-segmented to obtain an alignment mark according to the invention.

The alignment mark of Figure 7 makes alignment measurements on macro level and micro level with the same alignment mark and at the same location possible.

The invention may also be described by the following embodiments. Other aspects of the invention are set out as in the following numbered clauses: 1. An alignment mark to determine alignment of a first and a further exposure on a substrate on a macro level and a micro level, said alignment mark comprising a first alignment pattern projected during the first exposure and a second alignment pattern projected during the further exposure, wherein said alignment mark comprises a first sub-mark at least partially defined by said first alignment pattern and a second sub-mark at least partially defined by said second alignment pattern, wherein relative positions of said first and second sub-marks on said substrate are representative for alignment of the first and further exposures on the macro level, and wherein at least one submark is at least partially defined by image lines of said first alignment pattern and said second alignment pattern, wherein a part of the image lines is projected during the first exposure and a part of the image lines is projected during the further exposure, and wherein relative positions of image lines of said first alignment pattern and image lines of said second alignment pattern of said at least one sub-mark are representative for alignment of the first and further exposures on the micro level.

2. The alignment mark of embodiment 1, wherein said at least one sub-mark is said first submark or said second sub-mark.

3. The alignment mark of embodiment 1, wherein each of said first sub-mark and said second sub-mark are defined by image lines of said first alignment pattern and said second alignment pattern.

4. The alignment mark of embodiment 1, wherein, in said at least one sub-mark, image lines of one of said first and second alignment pattern enclose lines of the other alignment pattern.

5. The alignment mark of embodiment 1, wherein, in said at least one sub-mark, image lines of one of said first and second alignment pattern define an array of rectangular cells, and lines of the other of said first and second alignment pattern define a line within each of said rectangular cells.

6. The alignment mark of embodiment 1, wherein the first exposure and the further exposure are part of a double patterning process.

7. The alignment mark of embodiment 1, wherein said micro level is substantially the same as the projection resolution on said substrate.

8. The alignment mark of embodiment 1, wherein said micro level is in a range smaller than 150 nm, preferably between 5 nm and 100 nm.

9. The alignment mark of embodiment 1, wherein said macro level is in a range larger than 200 nm, preferably between 0,5 pm and 50 pm.

10. The alignment mark of embodiment 1, wherein a width of the first and second sub-mark is larger than 200 nm, preferably between 0,5 pm and 5 pm.

11. The alignment mark of clause 1, wherein the width of the sub-marks is between 0,5 μιη and 5 μιη.

12. A substrate comprising the alignment mark of any of the embodiment 1-11.

13. Set of patterning devices for use in a lithographic process, comprising: a first patterning device having a first alignment pattern to be projected on a substrate during a first exposure as part of an alignment mark, and a second patterning device having a second alignment pattern to be projected on said substrate during a further exposure as part of the same alignment mark, wherein said first alignment pattern at least partially defines a first sub-mark of said alignment mark, and wherein said second alignment pattern at least partially defines a second sub-mark of said alignment mark, wherein relative positions of the first and second sub-marks on said substrate are suitable to determine alignment of the first and further exposures on macro level, and wherein said first alignment pattern and said second alignment pattern in combination define at least one sub-mark, which is at least partially defined by image lines of said first alignment pattern and said second alignment pattern, wherein a part of the image lines is projected during the first exposure and a part of the image lines is projected during the further exposure, and wherein relative positions of image lines of said first alignment pattern and said second alignment pattern of said at least one sub-mark on said substrate are suitable to determine alignment of the first and further exposures on micro level.

14. The set of patterning devices of embodiment 13, wherein the alignment mark comprises any of the features of the embodiments 1-11.

15. A device manufacturing method comprising: transferring during a first exposure a pattern from a first patterning device onto a substrate, transferring during a further exposure a pattern from a second patterning device onto said substrate, wherein said first patterning device comprises a first alignment pattern projected during said first exposure as part of an alignment mark on said substrate, and wherein said second patterning device comprises a second alignment pattern projected during the further exposure as part of the same alignment mark, wherein said first alignment pattern at least partially defines a first sub-mark of said alignment mark, and wherein said second alignment pattern at least partially defines a second sub-mark of said alignment mark, and wherein said first alignment pattern and said second alignment pattern in combination define at least one sub-mark, determining alignment of the first and further exposures on macro level by comparison of relative positions of the first and second sub-marks on said substrate, and determining alignment of the first and further exposures on micro level by comparison of relative positions of image lines of said first alignment pattern and said second alignment pattern within said at least one sub-mark on said substrate.

16. The method of embodiment 15, wherein the first and further exposure are part of a double patterning process.

17. The method of embodiment 15, wherein the alignment mark comprises any of the features of the embodiments 1-11.

19. The method of embodiment 15, wherein a photo-resistive layer is arranged on the substrate between the first and further exposure.

Although specific reference may be made in this text to the use of lithographic apparatus in the manufacture of ICs, it should be understood that the lithographic apparatus described herein may have other applications, such as the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat-panel displays, liquid-crystal displays (LCDs), thin-film magnetic heads, etc. The skilled artisan will appreciate that, in the context of such alternative applications, any use of the terms “wafer” or “die” herein may be considered as synonymous with the more general terms “substrate” or “target portion", respectively. The substrate referred to herein may be processed, before or after exposure, in for example a track (a tool that typically applies a layer of resist to a substrate and develops the exposed resist), a metrology tool and/or an inspection tool. Where applicable, the disclosure herein may be applied to such and other substrate processing tools. Further, the substrate may be processed more than once, for example in order to create a multi-layer TC, so that the term substrate used herein may also refer to a substrate that already contains multiple processed layers.

Although specific reference may have been made above to the use of embodiments of the invention in the context of optical lithography, it will be appreciated that the invention may be used in other applications, for example imprint lithography, and where the context allows, is not limited to optical lithography. In imprint lithography a topography in a patterning device defines the pattern created on a substrate. The topography of the patterning device may be pressed into a layer of resist supplied to the substrate whereupon the resist is cured by applying electromagnetic radiation, heat, pressure or a combination thereof. The patterning device is moved out of the resist leaving a pattern in it after the resist is cured.

The terms “radiation” and “beam” used herein encompass all types of electromagnetic radiation, including ultraviolet (UV) radiation (e.g. having a wavelength of or about 365, 248, 193, 157 or 126 nm) and extreme ultra-violet (EUV) radiation (e.g. having a wavelength in the range of 5-20 nm), as well as particle beams, such as ion beams or electron beams.

The term “lens”, where the context allows, may refer to any one or combination of various types of optical components, including refractive, reflective, magnetic, electromagnetic and electrostatic optical components.

While specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described. For example, the invention may take the form of a computer program containing one or more sequences of machine-readable instructions describing a method as disclosed above, or a data storage medium (e.g. semiconductor memory, magnetic or optical disk) having such a computer program stored therein.

The descriptions above are intended to be illustrative, not limiting. Thus, it will be apparent to one skilled in the art that modifications may be made to the invention as described without departing from the scope of the clauses set out below.

Claims

A lithography device comprising: an exposure device adapted to provide a radiation beam; a carrier constructed to support a patterning device, the patterning device being capable of applying a pattern in a cross-section of the radiation beam to form a patterned radiation beam; a substrate table constructed to support a substrate; and a projection device adapted to project the patterned radiation beam onto a target area of the substrate, characterized in that the substrate table is adapted to position the target area of the substrate in a focal plane of the projection device.